PHP Socket Server? What the pcntl_fork are streams!

By

Christopher Langton

@chrisdlangton

Source Code

{
  "require": {
    "php": "^7.0",
    "sockets/php-stream-socket-server": "^1.4"
  }
}

pcntl_fork

When called from a running process pcntl_fork will open a new process on the operating system which will continue to execute in parallel.

Consider:

Tick syntax

Have you seen the declare function used like this before?

This produces only 1 output, because a tick occurs 1 time per statement, and zend counts ; and {} blocks as a statement.

declare(ticks=1) {{ echo 'tick'; }}
How many ticks printed?

How many printed here?
function tickFunc() { echo 'tick'; }
register_tick_function("tickFunc");
declare(ticks=2);

Ticks cont..

Why do we care about ticks?

• They loosely correspond to the statements in your script

  When we fork this can cause unexpected execution blocks internally

• You can register functions to execute when a tick occurs

  Great for profiling and debugging, as well as checking resources like mysql are alive

• You can control how many statements it takes to set off a tick

  We want this set to 1 statement per tick

You'll encounter some pretty crazy unjustifiable scenarios when forking and leaving zend-ng to figure out statement blocks

Streams

Stream Syntax

const SOCKET_WAIT = 
            0;
// open a tcp socket on specified open port
$socket = stream_socket_server('tcp://domain:port', $errNo, $errStr);
// zero blocks this process, waits indefinately until a client connects

// errors return as false and complete the while loop
    while ($connection = stream_socket_accept($socket, SOCKET_WAIT)) {
  // consume 1MB from the stream
    $message = stream_socket_recvfrom($connection, 1024);
  // peek this to not consume the data
  // use the message data, echo it back to the client
    fputs($connection, $message);
}
// Don't forget to disconnect sockets
    fclose($socket);
        

Putting it together

Questions?

References

• Process Forking
  php.net/manual/en/function.pcntl-fork
  
• Ticks
  php.net/manual/en/control-structures.declare
  
• Stream Sockets
  php.net/manual/en/function.stream-socket-accept
  
• Interprocess communitcation
  php.net/manual/en/function.stream-socket-pair
  
• Session leaders
  man7.org/linux/man-pages/man3/exit.3